17.alpha.-Haloethynyl-17.beta.-hydroxy steroids of the androstane and estrane series can be conventionally prepared by blocking 3- and 17.beta.-positioned oxygen functions of a 4(5)-unsaturated steroid, reacting the thus-obtained compound under reflux with potassium tertbutylate and a halogenating agent, such as N-bromosuccinimide in a tertiary alcohol, and then splitting off the blocking groups (DAS 1,242,607).
Another method uses trifluorobromomethane as the brominating agent; this compound is made to react in liquid ammonia with the lithium salt of the 17.alpha.-ethynyl steroid. Here, too, the oxygen functions on the C-3 atom and the 17.beta.-hydroxy group must be blocked [Tetrahedron 23:4111 (1967)].
Known 17.alpha.-iodoethynyl steroids thus far are only 17.alpha.-iodoethynyl-1,3,5(10)-estratriene-3,17.beta.-diol and its 11.beta.-methoxy derivative, obtained from 3-benzoyloxy-17.alpha.-ethynyl-1,3,5(10)-estratrien-17.beta.-ol and, respectively, from its 11.beta.-methoxy derivative by reaction with morpholine and iodine or with chloramine-T and sodium iodide and subsequent saponification of the 3-benzoyloxy group [J. Nucl. Med. 21:142 (1980)].